If a understand you question correctly, you are wanting to send CDR records over your LAN to a PC? You can do this if you are using Nortel's OTM software with the Telcom Billing package. On the PBX, you say yes to the BDI (Buffer Data Interface) prompt to tell the system to send the CDR records to a buffer area in memory. Then you configure OTM with the IP address of the PBX and it retrieves the CDR records in real time as they are generated. If the LAN connection drops, the records are stored in the buffer on the PBX until the LAN connection is restored or the buffer fills up. I'm not sure of the size.
If you don't have OTM, you could still have the PBX put the CDR records in the buffer, but I don't know how you would request the records be retrieved to a PC. I'm sure there is some command being issued to the PBX but I don't think it is documented anywhere.